For the Streusel:

1. Preheat oven to 350°F. Spray a 9×9 square baking pan with cooking spray, and line it with two small pieces of parchment paper. Set aside.
2. In a medium bowl, stir the melted butter, flour, light brown sugar, and cinnamon until combined. Crumble the mixture into small pieces. Set the streusel aside.

For the Coffee Cake:

1. Whisk the flour, pumpkin pie spice, baking powder, baking soda, and salt in a medium bowl until well mixed.
2. In a separate large bowl, add the oil, brown sugar, and sugar and use an electric mixer to beat until light and fluffy, about 3 minutes.
3. Mix in the pumpkin puree, sour cream and vanilla extract, then mix in the eggs one at a time until they are just incorporated.
4. Gradually mix in the dry ingredients at low speed, scraping the sides of the bowl occasionally to make sure all of the flour gets mixed in. Continue until everything is just combined. Be careful not to overmix the batter or the gluten will build up too much, and the crumb will be too tight.
5. Pour half of the batter into the prepared pan and spread it out evenly. Sprinkle half of the streusel over the bottom layer of batter evenly. Spoon the remaining batter over the streusel and carefully spread it out evenly. Top with the rest of the streusel. For more even layers, use a digital kitchen scale to weigh and divide the batter and streusel.
6. Bake the coffee cake for 45-50 minutes, or until a thin knife poked in the middle of the cake comes out clean or with a few small crumbs. Place the cake on a cooling rack to cool completely.

Maple Icing:

1. Stir the powdered sugar, maple syrup, and milk in a small bowl until smooth. Drizzle it over the cake. For a thicker icing, add 1 tablespoon of powdered sugar at a time until the desired consistency is reached. For a thinner icing, add 1 tablespoon of milk at a time.